Julia Gillard's closest supporter during her time as prime minister says the description of one of the Liberal Party's most senior women as a "bitch" shows Australia has made no progress in how it treats female MPs.

A shock decision by Industrial Relations Minister Kelly O'Dwyer to quit politics and spend more time with her young family triggered a torrent of abuse at the weekend, with some social media users describing the 42-year-old as a "bitch" and a "dog", and others posting slurs about her personal life.

Swinburne University has launched an investigation into one tweet by PhD candidate Philip Soos, who wrote "good riddance to this bitch" on Twitter and described the 42-year-old cabinet minister as a "filthy rat" who long opposed a royal commission into the banks. The university fielded a number of complaints about Mr Soos from staff and students.

Another post by the self-described 'Union News Australia' Facebook page featured an image with the words "bye bye, bitch!", which has since been deleted. ACTU secretary Sally McManus swiftly condemned the page and spent hours trying to have the post removed on Sunday.

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"It is not a union account. We would never say something like this. It's sexist," she said.

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Craig Emerson, a former cabinet minister under Julia Gillard, said Ms O'Dwyer and other women deserved better.

"I'm not someone who is into political correctness. I'm not someone who says 'you can't say anything that is critical or a bit unfair or even a bit hurtful'. But what I am saying is that the description of Kelly O'Dwyer or any woman as a bitch is absolutely sexist and, frankly, a verbal expression of violence against women," Mr Emerson said.

"There are no circumstances in which it is legitimate or reasonable for men to describe women as bitches.

"I will condemn it regardless of someone's political affiliations just as I condemned it when this sort of behaviour was displayed against Julia Gillard. It has been about eight years since then and there's no sign of improvement in my view, certainly not online or on Twitter."

Mr Emerson once said he felt physically sick when a number of Coalition MPs, including the then opposition leader Tony Abbott, stood in front of a placard at a rally outside Parliament with the words 'Ditch the Witch'. Another sign at the event called Ms Gillard "Bob Brown's Bitch" - a reference to her minority government agreement with the former Greens leader.

Julia Gillard was strongly defended by Craig Emerson against sexist attacks during her time as prime minister. Credit:Andrew Meares

"It seems to me that some people on Twitter - and it doesn't apply to everyone by any means - are engaged in a pretty vicious culture war between left and right and in this war it seems anything goes," Mr Emerson said.

"If we legitimise through indifference the description in public of women as bitches then we are in a sense normalising very poor behaviour that has some violent inferences. You don't call someone a bitch if you don't have a very nasty and angry streak in you.

"Kelly O'Dwyer and others don't deserve this and if we don't call it out, it will continue."

Mr Emerson said criticising Ms O'Dwyer's record as an MP and minister was fair game and noted much of the online reaction to her retirement announcement was focused on that.

Then opposition leader Tony Abbott in front of a "ditch the witch" poster at a rally outside Parliament House in 2011.Credit:Andrew Meares

When asked for comment, Mr Soos said: “I let my anger get the better of me against an elite politician who repeatedly blocked a vital RC into an industry that has harmed many men and women. Nevertheless, I recognise the tweet was improper and wrong, which is why I deleted it”.

A spokesman for Swinburne said the university was "investigating this incident".

"The university has detailed social media guidelines for current students and staff, asking for care and appropriate judgement when posting content on any social media platform," he said.

Ms O'Dwyer will not recontest her blue-ribbon inner Melbourne seat of Higgins at this year's election, citing a desire to spend more time with her two young children and try for a third with husband Jon.

An MP for 10 years and a cabinet minister since 2015, Ms O'Dwyer has held portfolio responsibilities for financial services, jobs, industrial relations and women.